strict-optional-properties error: Type 'Window & typeof globalThis' is not assignable to type 'Window'

[amcasey]

Bug Report

🔎 Search Terms

strictoptionalproperties, global

⏯ Playground Link

Playground link with relevant code (and enable strictOptionalProperties)

💻 Code

const w: Window = window;

🙁 Actual behavior

test.ts:1:7 - error TS2322: Type 'Window & typeof globalThis' is not assignable to type 'Window'.
  Types of property 'ontouchcancel' are incompatible.
    Type '(((this: GlobalEventHandlers, ev: TouchEvent) => any) & ((this: Window, ev: TouchEvent) => any)) | null | undefined' is not assignable to type '((this: GlobalEventHandlers, ev: TouchEvent) => any) | null'.
      Type 'undefined' is not assignable to type '((this: GlobalEventHandlers, ev: TouchEvent) => any) | null'.

1 const w: Window = window;
        ~

🙂 Expected behavior

Usually, T & U is assignable to T.

[DanielRosenwasser]

CC @ahejlsberg - it is kind of weird that optional properties on Window don't have corresponding optionality on globals (#36057).

It sounds like the "easiest" workaround is just to mark all the optional properties/methods in the DOM as | undefined.

[amcasey]

I think fixing the new errors in https://github.com/mui-org/material-ui might be a useful exercise. It looks like there are going to be some issues for consumers of @types/react if we don't seed an update.

[sandersn]

Fixed by microsoft/TypeScript-DOM-lib-generator#1092 and subsequently #45324